U.S. patent number 8,275,330 [Application Number 12/895,255] was granted by the patent office on 2012-09-25 for radio frequency transmitter energy shifting during ramp-down.
This patent grant is currently assigned to RF Micro Devices, Inc.. Invention is credited to Alexander Wayne Hietala, Nadim Khlat.
United States Patent |
8,275,330 |
Khlat , et al. |
September 25, 2012 |
Radio frequency transmitter energy shifting during ramp-down
Abstract
The present disclosure relates to IQ modulation circuitry that
during a data burst mode, modulates an RF carrier signal to provide
a modulated RF signal, which is used for transmission of a transmit
slot. During the data burst mode, a maximum energy spectrum peak of
the modulated RF signal is about coincident with an RF carrier
frequency of the RF carrier signal to comply with communications
protocols. Further, during an energy-shifted ramp-down mode, which
is coincident with ramp-down of the modulated RF signal, the IQ
modulation circuitry modulates the RF carrier signal to provide the
modulated RF signal. During the energy-shifted ramp-down mode, the
maximum energy spectrum peak of the modulated RF signal is shifted
away from the RF carrier frequency of the RF carrier signal to
mitigate the effects of preparing for receiving an RF receive
signal.
Inventors: |
Khlat; Nadim (Cugnaux,
FR), Hietala; Alexander Wayne (Phoenix, AZ) |
Assignee: |
RF Micro Devices, Inc.
(Greensboro, NC)
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Family
ID: |
46846370 |
Appl.
No.: |
12/895,255 |
Filed: |
September 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61247376 |
Sep 30, 2009 |
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Current U.S.
Class: |
455/127.1;
375/296 |
Current CPC
Class: |
H04B
1/0475 (20130101) |
Current International
Class: |
H04B
1/04 (20060101) |
Field of
Search: |
;455/91,114.1,114.2,114.3,115.1,116,118,126,127.1,127.4,127.5
;375/295,296,302 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Le; Thanh
Attorney, Agent or Firm: Withrow & Terranova,
P.L.L.C.
Parent Case Text
This application claims the benefit of provisional patent
application Ser. No. 61/247,376, filed Sep. 30, 2009, the
disclosure of which is hereby incorporated herein by reference in
its entirety.
Claims
What is claimed is:
1. Radio frequency (RF) circuitry comprising: control circuitry
adapted to select one of a plurality of operating modes, such that
the plurality of operating modes comprises a data burst mode, and
an energy-shifted ramp-down mode; and IQ modulation circuitry
adapted to: during the data burst mode, modulate an RF carrier
signal having an RF carrier frequency to provide a modulated RF
signal, such that a maximum energy spectrum peak of the modulated
RF signal is about coincident with the RF carrier frequency; and
during the energy-shifted ramp-down mode, modulate the RF carrier
signal to provide the modulated RF signal, such that the maximum
energy spectrum peak is shifted away the RF carrier frequency.
2. The RF circuitry of claim 1 wherein during the energy-shifted
ramp-down mode: the maximum energy spectrum peak is associated with
an energy spectrum of the modulated RF signal; and an energy level
of the energy spectrum at the RF carrier frequency is at least 10
decibels (dB) less than the maximum energy spectrum peak.
3. The RF circuitry of claim 1 wherein during the energy-shifted
ramp-down mode: the maximum energy spectrum peak is associated with
an energy spectrum of the modulated RF signal; and an energy level
of the energy spectrum at the RF carrier frequency is at least 20
decibels (dB) less than the maximum energy spectrum peak.
4. The RF circuitry of claim 1 wherein: the plurality of operating
modes further comprises a standard ramp-down mode and a ramp-up
mode; the ramp-up mode is immediately followed by the data burst
mode; and the standard ramp-down mode is immediately preceded by
the data burst mode.
5. The RF circuitry of claim 1 further comprising RF
down-conversion circuitry adapted to during a receive mode, receive
and down-convert an RF receive signal to provide a baseband receive
signal, such that RF power amplifier circuitry is adapted to during
the data burst mode and the energy-shifted ramp-down mode, receive
and amplify the modulated RF signal to provide an RF transmit
signal, wherein the plurality of operating modes further comprises
the receive mode.
6. The RF circuitry of claim 5 wherein a carrier frequency of the
RF transmit signal is about equal to a carrier frequency of the RF
receive signal.
7. The RF circuitry of claim 6 wherein the RF down-conversion
circuitry comprises direct current (DC) offset correction circuitry
adapted to: during the energy-shifted ramp-down mode and a receive
preparation mode, measure a DC offset of the RF down-conversion
circuitry to obtain a measured DC offset; and during the receive
mode, apply a DC offset correction to the RF down-conversion
circuitry based on the measured DC offset, wherein the plurality of
operating modes further comprises the receive preparation mode.
8. The RF circuitry of claim 7 wherein a bandwidth of the DC offset
correction circuitry is wider during the receive preparation mode
than during the energy-shifted ramp-down mode.
9. The RF circuitry of claim 6 further comprising a common
frequency synthesizer adapted to: during the data burst mode,
provide the RF carrier signal to an IQ modulator to create the
modulated RF signal; and during the energy-shifted ramp-down mode,
provide an RF local oscillator (LO) signal to the RF
down-conversion circuitry, such that the RF carrier signal to
provide the modulated RF signal adjusts a frequency of the RF LO
signal to correspond to a desired receive frequency of the RF
receive signal to compensate for pulling of the common frequency
synthesizer; and during the receive mode, provide the RF LO signal
to the RF down-conversion circuitry for down-conversion of the RF
receive signal, such that the frequency of the RF LO signal
corresponds to the desired receive frequency of the RF receive
signal.
10. The RF circuitry of claim 6 further comprising: a receive
frequency synthesizer adapted to: during the energy-shifted
ramp-down mode, provide an RF local oscillator (LO) signal to the
RF down-conversion circuitry, such that a frequency of the RF LO
signal corresponds to a desired receive frequency of the RF receive
signal; and during the receive mode, provide the RF LO signal to
the RF down-conversion circuitry for down-conversion of the RF
receive signal, such that the frequency of the RF LO signal
corresponds to the desired receive frequency of the RF receive
signal; and a transmit frequency synthesizer adapted to: during the
data burst mode, provide the RF carrier signal to an IQ modulator
to create the modulated RF signal; and during the energy-shifted
ramp-down mode, adjust the frequency of the RF LO signal to
correspond to the desired receive frequency of the RF receive
signal using the RF carrier signal to provide the modulated RF
signal to compensate for pulling of the receive frequency
synthesizer.
11. The RF circuitry of claim 6 wherein the RF transmit signal and
the RF receive signal are time division duplexing (TDD)
signals.
12. The RF circuitry of claim 11 wherein the RF transmit signal and
the RF receive signal are long term evolution (LTE) signals.
13. The RF circuitry of claim 11 wherein the RF transmit signal and
the RF receive signal are time division synchronous code division
multiple access (TD-SCDMA) signals.
14. The RF circuitry of claim 1 wherein during the energy-shifted
ramp-down mode, the RF carrier signal to provide the modulated RF
signal includes shifting a frequency of the RF carrier signal.
15. The RF circuitry of claim 1 wherein during the energy-shifted
ramp-down mode, the RF carrier signal to provide the modulated RF
signal includes amplitude modulating the RF carrier signal.
16. The RF circuitry of claim 1 wherein during the energy-shifted
ramp-down mode, the RF carrier signal to provide the modulated RF
signal includes phase modulating the RF carrier signal.
17. The RF circuitry of claim 1 wherein during the energy-shifted
ramp-down mode, the RF carrier signal to provide the modulated RF
signal includes amplitude modulating and phase modulating the RF
carrier signal.
18. The RF circuitry of claim 1 wherein during the energy-shifted
ramp-down mode, the RF carrier signal to provide the modulated RF
signal includes sending a string of data via the modulated RF
signal.
19. The RF circuitry of claim 18 wherein the string of data
includes alternating ones and zeros.
20. The RF circuitry of claim 1 wherein a duration of the
energy-shifted ramp-down mode is equal to between about 5.5 and
about 7.5 microseconds, and a duration of a receive preparation
mode is equal to between about 5 and about 7 microseconds, wherein
the plurality of operating modes further comprises the receive
preparation mode.
21. The RF circuitry of claim 1 wherein a duration of the
energy-shifted ramp-down mode is equal to about 6.5 microseconds
and a duration of a receive preparation mode is equal to about 6
microseconds, wherein the plurality of operating modes further
comprises the receive preparation mode.
22. The RF circuitry of claim 1 further comprising: RF power
amplifier circuitry adapted to during the data burst mode and the
energy-shifted ramp-down mode, receive and amplify the modulated RF
signal to provide an RF transmit signal; and RF down-conversion
circuitry adapted to during a receive mode, receive and
down-convert an RF receive signal to provide a baseband receive
signal, wherein the plurality of operating modes further comprises
the receive mode.
23. A method comprising: selecting one of a plurality of operating
modes, such that the plurality of operating modes comprises a data
burst mode, and an energy-shifted ramp-down mode; providing IQ
modulation circuitry; during the data burst mode, modulating an RF
carrier signal having an RF carrier frequency to provide a
modulated RF signal, such that a maximum energy spectrum peak of
the modulated RF signal is about coincident with the RF carrier
frequency; and during the energy-shifted ramp-down mode, modulating
the RF carrier signal to provide the modulated RF signal, such that
the maximum energy spectrum peak is shifted away the RF carrier
frequency.
Description
FIELD OF THE DISCLOSURE
Embodiments of the present disclosure relate to radio frequency
(RF) transmitters and associated modulation circuitry, RF
receivers, and RF frequency synthesizers, all of which may be used
in RF communications systems.
BACKGROUND OF THE DISCLOSURE
In time division duplex (TDD) RF communications systems, a
communications terminal may transmit and receive using a common
communications channel. Such transmissions and receptions are not
simultaneous and may share a common RF carrier frequency. In some
TDD protocols, a transmission may be shortly followed by a
reception with a guard period between the transmission and the
reception. However, with very short guard periods, the
communications terminal may have difficulty transitioning between
transmission and reception. FIGS. 1A and 1B illustrate a
transmission and reception scenario in which the communications
terminal sends a transmit slot 10, which is followed by a guard
period 12, which is followed by a receive slot 14 that is received
by the communications terminal according to the prior art. An
average amplitude 16 of an RF transmit signal sent from the
communications terminal has a ramp-up period 18, which is followed
by a data burst period 20 that is concurrent with transmission of
the transmit slot 10. The data burst period 20 is followed by a
ramp-down period 22, which may consume a significant portion of the
guard period 12. As such, the communications terminal continues to
transmit until completion of the ramp-down period 22. As a result,
since the remainder of the guard period 12 may be very short, the
communications terminal may have difficulty in preparing to receive
the receive slot 14.
In one example, if the communications terminal normally performs a
direct current (DC) offset correction of its receiver when
transitioning from transmit to receive, the remainder of the guard
period 12 may be too short to perform the DC offset correction.
Further, if the communications terminal performs the DC offset
correction at the beginning of the guard period 12, transmission
during the ramp-down period 22 may interfere with the DC offset
correction. In another example, when tuning a receive frequency
synthesizer in preparation to receive the receive slot 14, the
transmission during the ramp-down period 22 may pull a frequency of
the receive frequency synthesizer, such that the receiver is not
ready to receive the receive slot 14 at the end of the guard period
12. Thus, there is a need to mitigate the effects of transmitting
during the guard period 12 in preparation for receiving the receive
slot 14.
SUMMARY OF THE EMBODIMENTS
The present disclosure relates to IQ modulation circuitry that
during a data burst mode, modulates an RF carrier signal to provide
a modulated RF signal, which is used for transmission of a transmit
slot. During the data burst mode, a maximum energy spectrum peak of
the modulated RF signal is about coincident with an RF carrier
frequency of the RF carrier signal to comply with communications
protocols. Further, during an energy-shifted ramp-down mode, which
is coincident with ramp-down of the modulated RF signal, the IQ
modulation circuitry modulates the RF carrier signal to provide the
modulated RF signal. During the energy-shifted ramp-down mode, the
maximum energy spectrum peak of the modulated RF signal is shifted
away from the RF carrier frequency of the RF carrier signal to
mitigate the effects of preparing for receiving an RF receive
signal. In one embodiment of the IQ modulation circuitry, the
maximum energy spectrum peak of the modulated RF signal is shifted
away from the RF carrier frequency of the RF carrier signal to
allow DC offset correction of RF down-conversion circuitry. In an
alternate embodiment of the IQ modulation circuitry, the maximum
energy spectrum peak of the modulated RF signal is shifted away
from the RF carrier frequency of the RF carrier signal to
compensate for pulling of a frequency synthesizer, which provides
an RF local oscillator (LO) signal to the RF down-conversion
circuitry.
Those skilled in the art will appreciate the scope of the present
disclosure and realize additional aspects thereof after reading the
following detailed description of the preferred embodiments in
association with the accompanying drawing figures.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
The accompanying drawing figures incorporated in and forming a part
of this specification illustrate several aspects of the disclosure,
and together with the description serve to explain the principles
of the disclosure.
FIGS. 1A and 1B illustrate a transmission and reception scenario
according to the prior art.
FIG. 2 shows RF circuitry according to one embodiment of the RF
circuitry.
FIG. 3 shows details of baseband circuitry and RF front-end
circuitry illustrated in FIG. 1 according to one embodiment of the
baseband circuitry and the RF front-end circuitry.
FIG. 4 shows the RF circuitry according to an alternate embodiment
of the RF circuitry.
FIG. 5 shows the RF circuitry according to an additional embodiment
of the RF circuitry.
FIGS. 6A and 6B illustrate a transmission and reception scenario of
the RF circuitry illustrated in FIG. 3 according to one embodiment
of the RF circuitry.
FIGS. 7A and 7B illustrate a transmission and reception scenario of
the RF circuitry illustrated in FIG. 3 according to an alternate
embodiment of the RF circuitry.
FIGS. 8A and 8B show an energy spectrum of a modulated RF signal
according to one embodiment of the RF circuitry.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments set forth below represent the necessary information
to enable those skilled in the art to practice the disclosure and
illustrate the best mode of practicing the disclosure. Upon reading
the following description in light of the accompanying drawing
figures, those skilled in the art will understand the concepts of
the disclosure and will recognize applications of these concepts
not particularly addressed herein. It should be understood that
these concepts and applications fall within the scope of the
disclosure and the accompanying claims.
The present disclosure relates to IQ modulation circuitry that
during a data burst mode, modulates an RF carrier signal to provide
a modulated RF signal, which is used for transmission of a transmit
slot. During the data burst mode, a maximum energy spectrum peak of
the modulated RF signal is about coincident with an RF carrier
frequency of the RF carrier signal to comply with communications
protocols. Further, during an energy-shifted ramp-down mode, which
is coincident with ramp-down of the modulated RF signal, the IQ
modulation circuitry modulates the RF carrier signal to provide the
modulated RF signal. During the energy-shifted ramp-down mode, the
maximum energy spectrum peak of the modulated RF signal is shifted
away from the RF carrier frequency of the RF carrier signal to
mitigate the effects of preparing for receiving an RF receive
signal. In one embodiment of the IQ modulation circuitry, the
maximum energy spectrum peak of the modulated RF signal is shifted
away from the RF carrier frequency of the RF carrier signal to
allow DC offset correction of RF down-conversion circuitry. In an
alternate embodiment of the IQ modulation circuitry, the maximum
energy spectrum peak of the modulated RF signal is shifted away
from the RF carrier frequency of the RF carrier signal to
compensate for pulling of a frequency synthesizer, which provides
an RF local oscillator (LO) signal to the RF down-conversion
circuitry.
FIG. 2 shows RF circuitry 24 according to one embodiment of the RF
circuitry 24. The RF circuitry 24 includes baseband circuitry 26,
IQ modulation circuitry 28, which includes a transmit frequency
synthesizer 30 and an IQ modulator 32, RF front-end circuitry 34,
an antenna 36, RF down-conversion circuitry 38, and a receive
frequency synthesizer 40. The RF front-end circuitry 34 is coupled
to the antenna 36. The RF front-end circuitry 34 may provide an RF
receive signal RFRX, which was received via the antenna 36, to the
RF down-conversion circuitry 38. The RF down-conversion circuitry
38 may provide a baseband receive signal BBRX to the baseband
circuitry 26 based on receiving and down-converting the RF receive
signal RFRX. The baseband circuitry 26 may provide a transmit power
ramp signal VRAMP to the RF front-end circuitry 34. The baseband
circuitry 26 may provide a DC offset correction select signal DCOCS
to the RF down-conversion circuitry 38 to control DC offset
correction circuitry (not shown) in the RF down-conversion
circuitry 38. The baseband circuitry 26 may provide a receive
frequency select signal RXFSEL to the receive frequency synthesizer
40, which may provide an RF LO signal RFLOS to the RF
down-conversion circuitry 38 for use in down-conversion of the RF
receive signal RFRX. A frequency of the RF LO signal RFLOS may be
selected by the receive frequency select signal RXFSEL. The
baseband circuitry 26 may provide a transmit frequency select
signal TXFSEL to the transmit frequency synthesizer 30, which may
provide an RF carrier signal RFCAR to the IQ modulator 32. A
frequency of the RF carrier signal RFCAR may be selected by the
transmit frequency select signal TXFSEL. The baseband circuitry 26
may provide an in-phase modulation signal IMOD and a
quadrature-phase modulation signal QMOD to the IQ modulator 32. The
IQ modulator 32 may modulate the RF carrier signal RFCAR using the
in-phase modulation signal IMOD and the quadrature-phase modulation
signal QMOD to provide a modulated RF signal RFMOD to the RF
front-end circuitry 34.
FIG. 3 shows details of the baseband circuitry 26 and the RF
front-end circuitry 34 illustrated in FIG. 1 according to one
embodiment of the baseband circuitry 26 and the RF front-end
circuitry 34. The baseband circuitry 26 includes control circuitry
42 and the RF front-end circuitry 34 includes RF receiver circuitry
44, a DC-DC converter 46, and RF power amplifier circuitry 48. The
RF receiver circuitry 44 may receive and process RF signals from
the antenna 36 to provide the RF receive signal RFRX to the RF
down-conversion circuitry 38. The RF receiver circuitry 44 may
filter, amplify, switch, or any combination thereof, the received
RF signals from the antenna 36. The control circuitry 42 may
provide the transmit power ramp signal VRAMP to the DC-DC converter
46. The control circuitry 42 may provide the receive frequency
select signal RXFSEL, the transmit frequency select signal TXFSEL,
the in-phase modulation signal IMOD, and the quadrature-phase
modulation signal QMOD. The IQ modulator 32 provides the modulated
RF signal RFMOD to the RF power amplifier circuitry 48.
In general, the control circuitry 42 selects a frequency of the RF
carrier signal RFCAR via the transmit frequency select signal
TXFSEL, the IQ modulator 32 modulates the RF carrier signal RFCAR
to provide the modulated RF signal RFMOD to the RF power amplifier
circuitry 48, which receives and amplifies the modulated RF signal
RFMOD to provide an RF transmit signal RFTX to the antenna 36 for
transmission. The DC-DC converter 46 provides an envelope power
supply signal ENVPSS to the RF power amplifier circuitry 48 to
provide power for amplification. The envelope power supply signal
ENVPSS is based on the transmit power ramp signal VRAMP. In one
mode of operation, the transmit power ramp signal VRAMP may track
an amplitude ramp profile to cause the envelope power supply signal
ENVPSS to track the amplitude ramp profile. The control circuitry
42 selects a frequency of the RF LO signal RFLOS via the receive
frequency select signal RXFSEL, the RF down-conversion circuitry 38
receives and down-converts the RF receive signal RFRX using the RF
LO signal RFLOS to provide the baseband receive signal BBRX to the
baseband controller 26.
In one embodiment of the RF circuitry 24, the control circuitry 42
selects one of multiple operating modes. The multiple operating
modes may include any or all of a ramp-up mode, a data burst mode,
a standard ramp-down mode, an energy-shifted ramp-down mode, a
receive preparation mode, and a receive mode. During the data burst
mode, the RF circuitry 24 may transmit data via the RF transmit
signal RFTX, the control circuitry 42 may select an RF carrier
frequency of the RF carrier signal RFCAR via the transmit frequency
select signal TXFSEL, and the IQ modulation circuitry 28 may
modulate the RF carrier frequency of the RF carrier signal RFCAR to
provide the modulated RF signal RFMOD, such that a maximum energy
spectrum peak of the modulated RF signal RFMOD is about coincident
with the RF carrier frequency. During the data burst mode, the IQ
modulation circuitry 28 encodes the data to be transmitted by
modulating the RF carrier signal RFCAR using the in-phase
modulation signal IMOD and the quadrature-phase modulation signal
QMOD to provide the modulated RF signal RFMOD.
During the energy-shifted ramp-down mode, which may immediately
follow the data burst mode, the RF circuitry 24 has completed
sending a transmit slot. However, the RF circuitry 24 continues to
transmit via the RF transmit signal RFTX as an amplitude of the RF
transmit signal RFTX ramps down. Further, during the energy-shifted
ramp-down mode, the IQ modulation circuitry 28 modulates the RF
carrier signal RFCAR to provide the modulated RF signal RFMOD, such
that the maximum energy spectrum peak of the modulated RF signal
RFMOD is shifted away from the RF carrier frequency.
In a first embodiment of the IQ modulation circuitry 28, during the
energy-shifted ramp-down mode, the IQ modulation circuitry 28
modulates the RF carrier signal RFCAR to provide the modulated RF
signal RFMOD, such that the maximum energy spectrum peak of the
modulated RF signal RFMOD is shifted away from the RF carrier
frequency by shifting the RF carrier frequency of the RF carrier
signal RFCAR.
In a second embodiment of the IQ modulation circuitry 28, during
the energy-shifted ramp-down mode, the IQ modulation circuitry 28
modulates the RF carrier signal RFCAR to provide the modulated RF
signal RFMOD, such that the maximum energy spectrum peak of the
modulated RF signal RFMOD is shifted away from the RF carrier
frequency by amplitude modulating the RF carrier signal RFCAR.
In a third embodiment of the IQ modulation circuitry 28, during the
energy-shifted ramp-down mode, the IQ modulation circuitry 28
modulates the RF carrier signal RFCAR to provide the modulated RF
signal RFMOD, such that the maximum energy spectrum peak of the
modulated RF signal RFMOD is shifted away from the RF carrier
frequency by phase modulating the RF carrier signal RFCAR.
In a fourth embodiment of the IQ modulation circuitry 28, during
the energy-shifted ramp-down mode, the IQ modulation circuitry 28
modulates the RF carrier signal RFCAR to provide the modulated RF
signal RFMOD, such that the maximum energy spectrum peak of the
modulated RF signal RFMOD is shifted away from the RF carrier
frequency by amplitude modulating and phase modulating the RF
carrier signal RFCAR.
In a fifth embodiment of the IQ modulation circuitry 28, during the
energy-shifted ramp-down mode, the IQ modulation circuitry 28
modulates the RF carrier signal RFCAR to provide the modulated RF
signal RFMOD, such that the maximum energy spectrum peak of the
modulated RF signal RFMOD is shifted away from the RF carrier
frequency by sending a string of data via the modulated RF signal
RFMOD using the in-phase modulation signal IMOD and the
quadrature-phase modulation signal QMOD.
In a sixth embodiment of the IQ modulation circuitry 28, during the
energy-shifted ramp-down mode, the IQ modulation circuitry 28
modulates the RF carrier signal RFCAR to provide the modulated RF
signal RFMOD, such that the maximum energy spectrum peak of the
modulated RF signal RFMOD is shifted away from the RF carrier
frequency by sending a string of data via the modulated RF signal
RFMOD using the in-phase modulation signal IMOD and the
quadrature-phase modulation signal QMOD, such that the string of
data includes alternating ones and zeros.
In one embodiment of the control circuitry 42, the control
circuitry 42 selects the ramp-up mode immediately followed by the
data burst mode, which is immediately followed by the standard
ramp-down mode.
In an alternate embodiment of the control circuitry 42, the control
circuitry 42 selects the data burst mode, which is immediately
followed by the energy-shifted ramp-down mode, which is immediately
followed by the receive preparation mode, which is immediately
followed by the receive mode.
In one embodiment of the RF power amplifier circuitry 48, during
the data burst mode and during the energy-shifted ramp-down mode,
the RF power amplifier circuitry 48 receives and amplifies the
modulated RF signal RFMOD to provide the RF transmit signal RFTX.
In one embodiment of the RF down-conversion circuitry 38, during
the receive mode, the RF down-conversion circuitry 38 receives and
down-converts the RF receive signal RFRX to provide the baseband
receive signal BBRX. A carrier frequency of the RF transmit signal
RFTX may be about equal to a carrier frequency of the RF receive
signal RFRX. The RF transmit signal RFTX and the RF receive signal
RFRX may be time division duplexing (TDD) signals. The RF transmit
signal RFTX and the RF receive signal RFRX may be long term
evolution (LTE) signals. The RF transmit signal RFTX and the RF
receive signal RFRX may be time division synchronous code division
multiple access (TD-SCDMA) signals.
In one embodiment of the receive frequency synthesizer 40, during
the energy-shifted ramp-down mode, the receive frequency
synthesizer 40 provides the RF LO signal RFLOS to the RF
down-conversion circuitry 38, such that a frequency of the RF LO
signal RFLOS corresponds to a desired receive frequency of the RF
receive signal RFRX, and during the receive mode, the receive
frequency synthesizer 40 provides the RF LO signal RFLOS to the RF
down-conversion circuitry 38 for down-conversion of the RF receive
signal RFRX, such that the frequency of the RF LO signal RFLOS
corresponds to the desired receive frequency of the RF receive
signal RFRX.
In one embodiment of the transmit frequency synthesizer 30, during
the data burst mode, the transmit frequency synthesizer 30 provides
the RF carrier signal RFCAR to the IQ modulator 32 to create the
modulated RF signal RFMOD, and during the energy-shifted ramp-down
mode, the transmit frequency synthesizer 30 provides the RF carrier
signal RFCAR to the IQ modulator 32 to create the modulated RF
signal RFMOD and the IQ modulator 32 adjusts the frequency of the
RF LO signal RFLOS to correspond to the desired receive frequency
of the RF receive signal RFRX by modulating the RF carrier signal
RFCAR to compensate for pulling of the receive frequency
synthesizer 40, such that the maximum energy spectrum peak of the
modulated RF signal RFMOD is shifted away from the RF carrier
frequency.
FIG. 4 shows the RF circuitry 24 according to an alternate
embodiment of the RF circuitry 24. The RF circuitry 24 shown in
FIG. 4 is similar to the RF circuitry 24 illustrated in FIG. 3,
except in the RF circuitry 24 illustrated in FIG. 4, the RF
circuitry 24 includes a transceiver integrated circuit (IC) 50,
which includes the baseband circuitry 26, the IQ modulation
circuitry 28, the RF down-conversion circuitry 38, and the receive
frequency synthesizer 40. In the embodiment shown, the transceiver
IC 50 receives the RF receive signal RFRX and provides the
modulated RF signal RFMOD. In another embodiment (not shown) of the
RF circuitry 24, the RF circuitry 24 excludes the RF front-end
circuitry 34. Further, in the embodiment of the RF circuitry 24
shown in FIG. 4, the RF down-conversion circuitry 38 includes DC
offset correction circuitry 52, which receives the DC offset
correction select signal DCOCS. In one embodiment of the DC offset
correction circuitry 52, during the energy-shifted ramp-down mode
and the receive preparation mode, the DC offset correction
circuitry 52 measures a DC offset of the RF down-conversion
circuitry 38 to obtain a measured DC offset, and during the receive
mode, the DC offset correction circuitry 52 applies a DC offset
correction to the RF down-conversion circuitry 38 based on the
measured DC offset. A bandwidth of the DC offset correction
circuitry 52 during the receive preparation mode may be wider than
the bandwidth of the DC offset correction circuitry 52 during the
energy-shifted ramp-down mode.
FIG. 5 shows the RF circuitry 24 according to an additional
embodiment of the RF circuitry 24. The RF circuitry 24 illustrated
in FIG. 5 is similar to the RF circuitry 24 illustrated in FIG. 4,
except in the RF circuitry 24 illustrated in FIG. 5, the transmit
frequency synthesizer 30 and the receive frequency synthesizer 40
are both replaced with a common frequency synthesizer 54. The
common frequency synthesizer 54 receives the transmit frequency
select signal TXFSEL and the receive frequency select signal
RXFSEL, and provides the RF carrier signal RFCAR and the RF LO
signal RFLOS based on the transmit frequency select signal TXFSEL
and the receive frequency select signal RXFSEL, respectively.
In one embodiment of the common frequency synthesizer 54, during
the data burst mode, the common frequency synthesizer 54 provides
the RF carrier signal RFCAR to the IQ modulator 32 to create the
modulated RF signal RFMOD. During the energy-shifted ramp-down
mode, the common frequency synthesizer 54 provides the RF LO signal
RFLOS to the RF down-conversion circuitry 38, such that a frequency
of the RF LO signal RFLOS corresponds to a desired receive
frequency of the RF receive signal RFRX, and the common frequency
synthesizer 54 provides the RF carrier signal RFCAR to the IQ
modulator 32 to create the modulated RF signal RFMOD and the IQ
modulator 32 adjusts the frequency of the RF LO signal RFLOS to
correspond to the desired receive frequency of the RF receive
signal RFRX by modulating the RF carrier signal RFCAR to compensate
for pulling of the receive frequency synthesizer 40, such that the
maximum energy spectrum peak of the modulated RF signal RFMOD is
shifted away from the RF carrier frequency. During the receive
mode, the common frequency synthesizer 54 provides the RF LO signal
RFLOS to the RF down-conversion circuitry 38 for down-conversion of
the RF receive signal RFRX, such that the frequency of the RF LO
signal RFLOS corresponds to the desired receive frequency of the RF
receive signal RFRX.
FIGS. 6A and 6B illustrate a transmission and reception scenario of
the RF circuitry 24 illustrated in FIG. 3 according to one
embodiment of the RF circuitry 24. FIG. 6A shows the transmit slot
10, which is followed by the guard period 12, which is followed by
the receive slot 14. FIG. 6B shows an average amplitude 56 of the
RF transmit signal RFTX and shows a ramp-up mode 58, which is
followed by a data burst mode 60, which is followed by an
energy-shifted ramp-down mode 62, which is followed by a receive
preparation mode 64, which is followed by a receive mode 66. The
transmit slot 10 is transmitted during the data burst mode 60 by
the RF circuitry 24, the energy-shifted ramp-down mode 62 occurs
during a first portion of the guard period 12, the receive
preparation mode 64 occurs during a second portion of the guard
period 12, and the receive slot 14 is received by the RF circuitry
24 during the receive mode 66. The ramp-up mode 58 has a ramp-up
duration 68, the data burst mode 60 has a data burst duration 70,
the energy-shifted ramp-down mode 62 has a energy-shifted ramp-down
duration 72, the receive preparation mode 64 has a receive
preparation duration 74, and the receive mode 66 has a receive
duration 76. In a first exemplary embodiment of the RF circuitry
24, the energy-shifted ramp-down duration 72 is equal to between
about 5.5 microseconds and about 7.5 microseconds, and the receive
preparation duration 74 is equal to between about 5 microseconds
and about 7 microseconds. In a second exemplary embodiment of the
RF circuitry 24, the energy-shifted ramp-down duration 72 is equal
to about 6.5 microseconds, and the receive preparation duration 74
is equal to about 6 microseconds.
FIGS. 7A and 7B illustrate a transmission scenario of the RF
circuitry 24 illustrated in FIG. 3 according to an alternate
embodiment of the RF circuitry 24. FIG. 7A shows the transmit slot
10, which is not immediately followed by the guard period 12. As
such, the transmit slot 10 illustrated in FIG. 7A may be
transmitted by the RF circuitry 24 without the restrictions imposed
by the guard period 12. FIG. 7B shows an average amplitude 56 of
the RF transmit signal RFTX and shows the ramp-up mode 58, which is
followed by the data burst mode 60, which is followed by a standard
ramp-down mode 78 instead of the energy-shifted ramp-down mode 62.
The standard ramp-down mode 78 has a standard ramp-down duration
80.
FIGS. 8A and 8B show an energy spectrum of the modulated RF signal
RFMOD according to one embodiment of the RF circuitry 24. FIG. 8A
shows the energy spectrum of the modulated RF signal RFMOD during
the data burst mode 60 and FIG. 8B shows the energy spectrum of the
modulated RF signal RFMOD during the energy-shifted ramp-down mode
62. During the data burst mode 60, the energy spectrum of the
modulated RF signal RFMOD has a maximum energy spectrum peak 82
that is about coincident with an RF carrier frequency CF of the RF
carrier signal RFCAR as illustrated in FIG. 8A. During the
energy-shifted ramp-down mode 62, the energy spectrum of the
modulated RF signal RFMOD has a maximum energy spectrum peak 82
that is shifted away from the RF carrier frequency CF of the RF
carrier signal RFCAR as illustrated in FIG. 8B. The maximum energy
spectrum peak 82 occurs at a shifted frequency SF. As a result,
there is a difference 84 between an energy level of the energy
spectrum at the maximum energy spectrum peak 82 and an energy level
of the energy spectrum at the RF carrier frequency CF. The energy
level of the energy spectrum at the RF carrier frequency CF is less
than the energy level of the energy spectrum at the maximum energy
spectrum peak 82. In a first exemplary embodiment of the RF
circuitry 24, the difference 84 is at least 10 decibels (dB). In a
second exemplary embodiment of the RF circuitry 24, the difference
84 is at least 20 dB.
Some of the circuitry previously described may use discrete
circuitry, integrated circuitry, programmable circuitry,
non-volatile circuitry, volatile circuitry, software executing
instructions on computing hardware, firmware executing instructions
on computing hardware, the like, or any combination thereof. The
computing hardware may include mainframes, micro-processors,
micro-controllers, DSPs, the like, or any combination thereof.
None of the embodiments of the present disclosure are intended to
limit the scope of any other embodiment of the present disclosure.
Any or all of any embodiment of the present disclosure may be
combined with any or all of any other embodiment of the present
disclosure to create new embodiments of the present disclosure.
Those skilled in the art will recognize improvements and
modifications to the preferred embodiments of the present
disclosure. All such improvements and modifications are considered
within the scope of the concepts disclosed herein and the claims
that follow.
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